Acral lentiginous melanoma. A histological type without prognostic significance

Acral lentiginous melanoma (ALM) is reported to have a poorer prognosis than melanomas of other histotypes.

The purpose of this paper is to verify if ALMs, per se, have a more aggressive behavior or if the poorer prognosis of these patients is due to a later diagnosis.

Clinical charts of 165 patients with acrally located melanoma were reviewed as well as all histological slides. In all patients, histotype, Clark's level, Breslow thickness, pigmentation, presence of ulceration, and regression were reported. Mitotic index, vascular invasion, and microscopic satellitosis were also determined. Survival of the 64 patients with ALM was compared with survival observed in the remaining 101 acral (nonlentiginous) melanomas.

Melanoma localized at acral sites constitute 8.9% of the 1845 patients with melanoma treated at our Institute from 1975 to 1990. All were Caucasian, 57 were males, and 108 females. Out of the 165 patients with this localization, 64 (38.8%) were classified as ALM. Disease-free and overall survival of the 64 ALM patients were not different at a statistically significant level compared with the areas observed in the other acral nonlentiginous melanoma.

The survival difference between ALM and other histological types is due to a later diagnosis and not to a more aggressive behavior of ALM.